"The asset class does play a role. It's not just bad manager performance," said Joanna Pratt, vice president of financial markets at Nerd Wallet, a financial markets and investing information site. "You really can't know ahead of time what those bad asset classes are doing to be in the next five to 10 years, so it's really important to have a diversified portfolio."

Nerd Wallet listed what it considers to be the 12 worst-performing mutual funds based on fees and performance. They are (with five-year annualized returns and net expense ratios):

Pratt said investors should take a hard look at expense ratios and consider that most active managers do not achieve basic market returns.

"Statistically, active managers tend to underperform the index," Pratt said. "Over the past 10 years, only 24 percent of actively managed funds outperformed the index, and they tend to charge higher fees. We would just caution investors when looking to pay higher expense ratios that the math just doesn't support that."

Mutual fund investing still dominates but has been on the decline over the past several years as exchange-traded funds have surged in popularity and now hold $1.5 trillion in assets under management.